Acrylate rubber vulcanizable compositions

ABSTRACT

Acrylate rubbers having both halogen and carboxyl cure sites are vulcanized using an alkali metal salt of a carboxylic or organo-phosphoric acid and an amine-blocked isocyanate. The vulcanized compositions exhibit low press-cured and post-cured compression set.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of application Ser. No. 453,278, now U.S.Pat. No. 3,912,672, filed on Mar. 21, 1974, which is a continuation ofapplication Ser. No. 272,849 filed on July 18, 1972, and now abandoned.

BACKGROUND OF THE INVENTION

Acrylate rubbers exhibit very favorable qualities of weatherability,high temperature serviceability, and good oil resistance. Thesequalities make the rubbers useful for under-the-hood automotiveapplications and out-of-door applications. Their use is limited by thetendency of the vulcanizates to post-cure during use. This results inproperty change and in some cases in failure of the article. To overcomethese problems, the acrylate rubber vulcanizates are purposelypost-cured, often as long as 24 hours or more, to obtain a more completecure. This is shown by a reduced compression set. It would be of greatadvantage to the industry to reduce the time required for, or eliminatethe need of, post-cure for the acrylate rubber vulcanizates.

Much effort has gone into the development of both faster and moreefficient cures of acrylate rubbers. An article in Rubber Chemistry andTechnology, Vol. 44, No. 2 (1971), traces the more recent efforts.Various cure sites and cure systems have been evaluated; see U.S. Pat.Nos. 3,288,763; 3,324,088; 3,337,492; 3,435,010; 3,450,681 and3,458,461. However, the need for a long post-cure has not beeneliminated, and improved vulcanizates are desired.

SUMMARY OF THE INVENTION

Compositions comprising an acrylate rubber having both halogen andcarboxyl cure sites and, as the only curatives, (a) an alkali metal saltof a carboxylic or organo-phosphoric acid, and (b) an amine-blockedisocyanate are readily cured to vulcanizates having improved press-cureand post-cure compression set.

DETAILED DESCRIPTION

The acrylate rubbers are interpolymers comprising acrylate monomer(s), areactive halogen-containing monomer, and a carboxyl-containing monomer.

The acrylate rubber contains from about 40% to about 99.8% by weight,based upon the weight of the polymer, of an acrylate or mixtures ofacrylates of the formula ##STR1## wherein R' is an alkyl radicalcontaining 1 to 18 carbon atoms, an alkoxyalkyl or alkylthioalkylradical containing a total of 2 to about 12 carbon atoms, or acyanoalkyl radical containing 2 to about 12 carbon atoms. The alkylstructure can contain primary, secondary, or tertiary carbonconfigurations. Examples of such acrylates are methyl acrylate, ethylacrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentylacrylate, isoamyl acrylate, n-hexyl acrylate, 2-methyl-pentyl acrylate,n-octyl acrylate, 2-ethylhexyl acrylate, n-decyl acrylate, n-dodecylacrylate, n-octadecyl acrylate, and the like; methoxymethyl acrylate,methoxyethyl acrylate, ethoxyethyl acrylate, butoxyethyl acrylate,ethoxypropyl acrylate, methylthioethyl acrylate, hexylthioethylacrylate, and the like; and α and β-cyanoethyl acrylate, α, β, andγ-cyanopropyl acrylate, cyanobutyl acrylate, cyanohexyl acrylate,cyanooctyl acrylate, and the like. Often mixtures of two or more typesof acrylate monomers are employed.

Preferredly, the rubber contains from about 65% to about 99.6% by weightof an acrylate or mixtures of acrylates, of the formula wherein R' is analkyl radical containing 1 to about 10 carbon atoms or an alkoxyalkylradical containing 2 to about 8 carbon atoms. Examples of the morepreferred acrylates are ethyl acrylate, propyl acrylate, n-butylacrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, and thelike, and methoxyethyl acrylate, ethoxyethyl acrylate, and the like.Both an alkyl acrylate and an alkoxyalkyl acrylate can be used inadmixture.

The rubber contains from about 0.1% to about 30% by weight of an activehalogen-containing monomer(s). The halogen groups can be chlorine,bromine, or iodine. The monomers are of two main types,halogen-containing vinylidene hydrocarbons and halogen-containing vinylmonomers having the halogen group at least 2 carbon atoms removed froman oxygen atom(s). Examples of halogen-containing vinylidenehydrocarbons are vinyl benzyl chloride, vinyl benzyl bromide,5-chloromethyl-2-norbornene, 5-bromomethyl-2-norbornene,5-β-chloroethyl-2-norbornene, and the like. The second type of monomer,i.e., those having the halogen group at least 2 carbon atoms removedfrom an oxygen atom, are characterized by having ether (-O-), ketone##STR2## or ester ##STR3## structures in the monomer where the halogengroup is at least 2 carbon atoms and up to 6 or more carbon atomsremoved from an oxygen atom. Examples of these monomers arehalogen-containing vinyl esters such as vinyl chloroacetate, vinylbromoacetate, allyl chloroacetate, vinyl 3-chloropropionate, vinyl4-chlorobutyrate, vinyl 4-bromobutyrate, and the like;halogen-containing acrylates such as 2-chloroethyl acrylate,3-chloropropyl acrylate, 4-chlorobutyl acrylate, 2-chloroethylmethacrylate, 2-bromoethyl acrylate, 2-iodoethyl acrylate,4-chloro-2-butenyl acrylate, 2-chloroacetoxyethyl acrylate andmethacrylate, and the like; halogen-containing vinyl ethers such as2-chloroethyl vinyl ether; halogen-containing vinyl ketones such aschloromethyl vinyl ketone, 2-chloroethyl vinyl ketone, and the like; and5-chloroacetoxymethyl-2-norbornene,5-(α,β-dichloropropionylmethyl)-2-norbornene, and the like.

The more preferred halogen-containing monomers are vinyl benzylchloride, 5-chloromethyl-2-norbornene, vinyl chloroacetate,2-chloroethyl acrylate, and 5-(α-chloroacetoxymethyl)-2-norbornene.

More preferredly, the rubber contains from about 0.2% to about 15% byweight of the halogen-containing monomer. At this level, the halogencontent is from about 0.1% to about 5% by weight of the rubber. Due toavailability and cost, the chlorine-containing monomers are preferred.

The rubbers also contain from about 0.1% to about 20% by weight of acarboxyl-containing monomer(s). The monomer can be monocarboxylic orpolycarboxylic, containing from 3 to about 8 carbon atoms. Examples ofsuch monomers are acrylic acid, methacrylic acid, ethacrylic acid,β,β-dimethyl acrylic acid, crotonic acid, 2-pentenoic acid, 2-hexenoicacid, maleic acid, fumaric acid, citraconic acid, mesaconic acid,itaconic acid, 3-butene-1,2,3-tricarboxylic acid, and the like.

More preferably, the rubber contains from about 0.2% to about 10% byweight of the carboxyl-containing monomer. At this level, the carboxylcontent is from about 0.1% to about 7% by weight of the rubber. The morepreferred monomers are the monocarboxylic acid monomers such as acrylicacid, methacrylic acid, itaconic acid, and the like.

The rubber can contain up to about 35% and preferably up to about 10% byweight of non-halogen-containing and non-carboxyl-containingcopolymerizable vinylidene monomers having a terminal vinylidene (CH₂=C<) group. Examples of such are phenyl acrylate, cyclohexyl acrylate,methacrylates, such as methyl methacrylate, ethyl methacrylate, and thelike; vinyl and allyl esters such as vinyl acetate, vinyl propionate,allyl acetate, and the like; vinyl ketones such as methyl vinyl ketone;vinyl and allyl ethers such as vinyl methyl ether, vinyl ethyl ether,allyl methyl ether, and the like; vinyl aromatics such as styrene,α-methyl styrene, vinyl toluene, and the like; vinyl nitriles such asacrylonitrile and methacrylonitrile; vinyl amides such as acrylamide,methacrylamide, N-methyl methacrylamide, and the like; and dienes anddivinyls such as butadiene, isoprene, divinyl benzene, divinyl ether,diethylene glycol diacrylate, and the like. The more preferredcopolymerizable monomers are vinyl acetate, allyl acetate, methylmethacrylate, ethyl methacrylate, vinyl ethyl ether, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide,divinyl benzene, and diethylene glycol diacrylate.

The acrylate rubbers can be prepared using emulsion (latex), suspension,solution, and bulk techniques known to those skilled in the art. Becauseit is desirable to polymerize the monomers to 90 percent conversion orover, emulsion and suspension techniques are usually employed. Thepolymerization can be performed as a batch reaction, or one or moreingredients can be proportioned during the run. Temperature ofpolymerization ranges from about -10°C. to about 100°C., whereas a morepreferred range is from about 5°C. to about 80°C.

The polymerization can be initiated by free-radical generating agents.Examples of such agents are organic peroxides and hydroperoxides such asbenzoyl peroxide, dicumyl peroxide, cumene hydroperoxide, paramethanehydroperoxide, and the like, used alone or with redox systems; diazocompounds such as azobisisobutyronitrile, and the like; persulfate saltssuch as sodium potassium, and ammonium persulfate, used alone or withredox systems; and the use of ultraviolet light with photo-sensitiveagents such as benzophenone, triphenylphosphine, organic diazos, and thelike.

Typical emulsion polymerization ingredients would include a persulfatesalt or organic peroxide and usually a redox system, water adjusted to adesired pH with acids or bases and usually buffered with inorganicsalts, and either anionic, cationic, or nonionic surface active agentswell known to the art.

The polymerization normally is continued until about 90% conversion ofmonomers is obtained. The resulting latex can be coagulated to isolatethe polymer. Typical coagulation procedures are salt/acid coagulations,use of polyvalent metal salts such as MgSO₄, use of alcohols such asmethanol and isopropyl alcohol, and freeze agglomeration techniques. Therubber is then usually washed with water and dried.

The acrylate rubbers are solid elastomers having a dilute solutionviscosity (DSV) of over 0.5 as measured on 0.2 gram of rubber in 100 ml.benzene at 25°C. Raw polymer Mooney values (ML-4 at 212°F.) are fromabout 20 to about 100.

The rubbers are admixed with cure ingredients and compoundingingredients using two-roll mills, internal mixers such as Banburys andextruders, and like equipment.

The acrylate rubbers can be vulcanized using known curatives. Examplesof these curatives are the soap-sulfur systems such as potassium andsodium stearate, sodium acetate, and potassium tartate with sulfur orsulfur donors such as dipentamethylene thiuram hexasulfide; polyaminessuch as hexamethylene diamine, triethylene diamine, triethylenetetraamine, and the like; and ammonium-carboxylic acid salts such asammonium benzoate, ammonium adipate, and ammonium stearate, used aloneor with alkyl halides such as dodecyl bromide. A disadvantage of thesecuratives is their failure to develop low compression set afterpress-cure.

It has been found that the acrylate rubbers of this invention arevulcanized efficiently in the absence of sulfur using an alkali metalsalt of a carboxylic or organophosphoric acid and an amine-blockedisocyanate. The press-cured and post-cured essentially sulfur-freevulcanizates exhibit comparatively lower compression set than knownvulcanizate compositions. This is achieved at no loss of desirableacrylate properties. Furthermore, the use of the amine-blockedisocyanate in the cure system yields increased scorch safety over theuse of an amine alone as a cure catalyst.

The carboxylic acid metal salt is used at a level from about 0.5 part toabout 7 parts by weight per 100 parts of rubber, and more preferredly,from about 1 part to about 5 parts by weight. The metal is an alkalimetal. The carboxylic acid is preferredly a monocarboxylic acidcontaining from 2 to about 24 carbon atoms. The acids may beunsaturated, and can contain hydroxy, ether, ester, or ketonic groups.Examples of such acids are acetic acid, propionic acid, isobutyric acid,valeric acid, caproic acid, octanoic acid, 2-ethyl hexanoic acid,decanoic acid, lauric acid, palmitic acid, stearic acid, cyclohexanecarboxylic acid, crotonic acid, cinnamic acid, hydroxy acetic acid,acetoacetic acid, butoxy acetic acid, levulinic acid, mono-3-octylmaleate, benzoic acid, phthalic acid, toluic acid, salicylic acid,naphthenic acid, and the like. More preferredly, the carboxylic acidcontains from about 6 to about 20 carbon atoms. Examples of the morepreferred monocarboxylic acids are octanoic acid, 2-ethyl hexanoic acid,decanoic acid, lauric acid, stearic acid, cinnamic acid, benzoic acid,toluic acid, naphthenic acid, and the like.

Preferredly, the metal salt is a salt of an alkyl or of an aromaticmonocarboxylic acid. Potassium and sodium are the preferred alkalimetals. Examples of the more preferred carboxylic acid metal salts aresodium octanoate, potassium 2-ethyl hexanoate, sodium t-dodecanoate,sodium and potassium tetradodecanoate, sodium and potassium stearate,sodium and potassium benzoate.

The alkali metal salts of organo-phosphoric acids also may be used atthe same levels of use as the metal salts of carboxylic acids. Thesecompounds are characterized by the structure ##STR4## wherein M is analkali metal, y = 1 or 2, z = 1 or 2, and y + z = 3, and R is an alkylradical containing 1 to 24 carbon atoms, an aryl radical containing 6 to24 carbon atoms, or a polyether as the condensation product of anorganic acid or alcohol with ethylene oxide. Examples of these compoundsare sodium salt of monophenyl phosphate, sodium salt ofmono-p-tert-butyl phenyl phosphate, potassium salt of di-o-xenylphosphate, sodium salt of mono-lauryl phosphate, sodium salt of dioctylphosphate, potassium salt of distearyl phosphate, potassium salt ofmonododecyl-monobenzyl phosphate, and sodium and potassium salts ofmono- and di-alkylphenoxy poly(ethyleneoxy) ethyl phosphates. Morepreferredly, M is sodium or potassium and R, when an alkyl radical,contains about 8 to about 18 carbon atoms, and, when an aryl radical,contains 6 to about 14 carbon atoms.

The amine-blocked isocyanates are used as cure catalysts in thecompositions. Upon heating to vulcanization temperatures, theamine-blocked isocyanates decompose to yield free amine which catalyzesthe cure of the acrylate rubber. The use of amine-blocked isocyanates inplace of free amine in the compositions provides for increased scorchsafety. The amine-blocked isocyanates are employed in levels from about0.1 part to about 10 parts by weight per 100 parts by weight of acrylaterubber. More preferredly, they are used in from about 0.3 part to about5 parts by weight.

Amine-blocked isocyanates are known to the art (see U.S. Pat. Nos.3,238,010 and 3,300,431). They are prepared by reacting an amine with amono-, di- or polyisocyanate. Simply contacting the amine andisocyanate, usually in a solvent or diluent, is sufficient to prepare anamine-blocked isocyanate. The reaction can be represented as follows:##STR5## wherein R is a hydrocarbon group and R' is a hydrocarbon groupwhich can contain further isocyanate (-NCO) groups.

The amines used to prepare the amine-blocked isocyanates are strongamines, having a dissociation (-log K) constant of below 10 (see Lange'sHandbook of Chemistry, 10th Edition, McGraw-Hill Book Co., N.Y. (1967),page 1213). The amines can be primary or secondary amines or guanidines,but more preferredly are secondary amines or guanidines.

The secondary amines can be aliphatic or aromatic amines, cyclicmethyleneamines, or heterocyclic amines. Examples of such amines aredimethylamine, diethylamine, diisopropyl amine, dioctyl amine, dilaurylamine, dibenzyl amine, methylbenzyl amine, methylethanol amine,diethanol amine, imidazole pyrrolidine, piperidine, piperazine,morpholine, and the like. The more preferred secondary amines are thedialkylamines wherein the alkyl group contains 1 to about 6 carbonatoms. Examples of the guanidines are guanidine, tetramethyl guanidine,dibutyl guanidine, diphenyl guanidine, diorthotolyl guanidine,dicyandiamide, and the like.

The isocyanates employed can be mono-, di-, or polyisocyanates. Examplesof the isocyanates are hexyl isocyanate, lauryl isocyanate, octadecylisocyanate, phenyl isocyanate, p-chlorophenyl isocyanate,m,p-dichlorophenyl isocyanate, 2,4- and 2,6-toluene diisocyanate,p-phenylene diisocyanate, bitolyl diisocyanate,diphenylmethane-p,p'-diisocyanate, diphenylmethane triisocyanate, andthe like. The more preferred isocyanates are the aromatic isocyanateswhich include phenyl isocyanates such as phenyl isocyanate,p-chlorophenyl isocyanate, m,p-dichlorophenyl isocyanate, and the like;aromatic diisocyanates such as 2,4- and 2,6-toluene diisocyanate,p-phenylene diisocyanate, and the like; and diphenyl diisocyanates suchas diphenylmethane-p,p'-diisocyanate, diphenylpropylidene diisocyanate,di(3-methylphenyl)-p,p'-diisocyanate, and the like.

Examples of amine-blocked isocyanates are dimethylamine/p-chloro- andm,p-dichlorophenyl isocyanate, dioctylamine/octadecyl isocyanate,dibenzylamine/hexyl isocyanate, morpholine/phenyl isocyanate,diphenylguanidine/tolyl isocyanate, dimethylamine/toluene diisocyanate,dicyandiamide/octadecyl isocyanate, diethylamine/toluene diisocyanate,dibutylamine/diphenylmethane diisocyanate, piperidine/bitolyldiisocyanate, pyrrolidine/diphenylmethane-p,p'-diisocyanate,di(tetramethyl guanidine)/toluene diisocyanate, and the like.

The acrylate rubbers can be admixed with many other rubber compoundingingredients. Examples of such ingredients are fillers such as the carbonblacks, calcium sulfates, aluminum silicates, phenol-formaldehyde andpolystyrene resins, asbestos, and the like; plasticizers and extenderssuch as dialkyl and diaryl organic esters like diisobutyl, diisooctyl,and dibenzyl sebacates, azelates, phthalates, and the like, petroleumoils, castor oil, tall oil, glycerin, and the like; antioxidants, andstabilizers such as phenyl-β-naphthylamine, 2,6-di-t-butyl paracresol,2,2'-methylenebis-(4-ethyl-6-t-butyl phenol),2,2'-thiobis-(4-methyl-6-t-butyl phenol),4,4'-butylidenebis-(6-t-butyl-m-cresol),tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate,tetrakismethylene-3(3',5'-di-t-butyl-4'-hydroxyphenyl)propionatemethane, distearyl thiodipropionate, tri(nonylatedphenyl) phosphite, andthe like; and other ingredients such as pigments, tackifiers, flameretardants, fungicides, and the like.

The novel compositions are cured at temperatures from about 250°F. toabout 450°F., whereas a more preferred range is from about 275°F. toabout 400°F. Cure time varies inversely as temperature, and ranges fromabout 1 minute to about 60 minutes or more. The polymers can bepost-cured for about 3 to 8 hours at a temperature from about 300°F. toabout 375°F.

The novel compositions develop rapid and stable cures. Full propertydevelopment is achieved faster than with previously known compositions.This is evidenced by the lower compression set values obtained afterpress-cure and post-cure. The vulcanizates were evaluated as to theirplied disk compression set (ASTM D395V), tensile and elongation (ASTMD412), hardness (ASTM D676-Durometer A), and Gehman Freeze (D1053). Curetimes were determined following ASTM D1646, using a Mooney Viscometer at250°F. with a large rotor, or using a Monsanto Rheometer or a B.F.G.Cone Curometer as described in U.S. Pat. No. 3,494,172.

The vulcanizates are useful in many applications where weatherability,high temperature serviceability and oil resistance are required. Suchapplications are under-the-hood automotive parts such as gaskets, seals,packings, belting and hosing, and out-of-doors applications such asweatherstripping, sealants, and hosing.

The following examples serve to more fully illustrate the invention.

EXAMPLE I

A polymer containing ethyl acrylate, n-butyl acrylate, methacrylic acid,and vinyl benzyl chloride was prepared using standard emulsionpolymerization techniques. The recipe used is as follows:

    Water, grams              2400                                                n-Butyl Acrylate, grams   1420                                                Ethyl Acrylate, grams     380                                                 Methacrylic Acid, grams   5.7                                                 Vinyl Benzyl Chloride, grams                                                                            20                                                  Gafac PE 510.sup.1, grams 35                                                  Daxad 17.sup.2, grams     9.5                                                 Sodium Sulfate, grams     5.7                                                 Diisopropylbenzene Hydroperoxide,                                                                       2.8                                                 milliliters.sup.3                                                             SFS.sup.4, milliliters.sup.5                                                                            3.6                                                 Sequestrene NaFe.sup.6, milliliters.sup.7                                                               2.0                                                 Na.sub.2 S.sub.2 O.sub.4, milliliters.sup.8                                                             15                                                  1 -       alkylphenoxy poly(ethyleneoxy)                                                ethyl phosphate                                                     2 -       polymerized alkyl naphthalene                                                 sulfonic acid                                                       3 -       1.4 milliliters catalyst in 10                                                milliliters acetone                                                 4 -       sodium formaldehyde sulfoxalate                                     5 -       5% by weight in water                                               6 -       sodium ferric ethylenediamine                                                 tetraacetic acid                                                    7 -       5% by weight in water                                               8 -       0.2% by weight in water                                         

The Gafac PE 510 was mixed in 200 grams of water and adjusted to a pH of6.5. The ethyl acrylate, n-butyl acrylate, methacrylic acid, and vinylbenzyl chloride were mixed together. 2200 grams of water was charged toa vessel which had been previously evacuated and purged with nitrogengas. One-half of the Gafac solution was added, followed by 190 grams ofthe monomer solution, the Daxad 17 and the sodium sulfate. The reactormix was cooled to 17°C. and the hydroperoxide, SFS, Sequestrene NaFe,and Na₂ S₂ O₄ added to initiate the reaction. Polymerization temperaturewas maintained at about 20°C. to 25°C. The remaining monomer solutionwas proportioned into the reactor over a 7-hour period. At 3.5 hoursinto the run, the remaining one-half of the Gafac solution was added.Total polymerization time was 10 hours. Percent conversion of monomersto polymer was above 95%. The emulsion was coagulated using a 25% byweight solution of NaCl in water, and methanol. The isolated polymer waswashed with water and dried. The polymer was a rubber having about a 30raw polymer Mooney value (M1-4, 212° F.).

The Example demonstrates that the polymers employed in this inventionare readily prepared using standard polymerization techniques. Thepolymers are just as easily prepared using suspension, solution, or bulkpolymerization procedures and techniques.

EXAMPLE II

Ethyl acrylate rubbers containing methacrylic acid and vinyl benzylchloride as cure site monomers were vulcanized using an alkali metalsalt of a carboxylic acid and an amine-blocked isocyanate as the curesystem. Two soap/sulfur cures of the rubber were run for a comparison.The rubber composition in percent by weight of interpolymerized monomerwas:

    Ethyl Acrylate            98.0                                                Vinyl Benzyl Chloride     1.6                                                 Methacrylic Acid          0.4                                             

The recipes used were as follows (in parts by weight):

                        1       2       3                                         Rubber              100     100     100                                       N550 Black          70      70      70                                        Acrawax C.sup.1     2       2       2                                         Sodium Stearate     3.5     3.5     3.5                                       Sulfur                                                                                            0.2     0.2                                               Amine-blocked iso-  1.0                                                       cyanate.sup.2                                                                 1 - synthetic wax                                                             2 - m,p-dichlorophenyl isocyanate                                               blocked with dimethylamine                                                                      1       2       3                                         Press Cure Conditions                                                         Time, minutes       8       8       8                                         Temperature, °F.                                                                           350     350     350                                       Tensile, psig       1520    800     750                                       Elongation, percent 210     430     360                                       Compression set,    73      95      94                                        percent - 70 hrs.                                                             at 300°F.                                                              Tempered Data                                                                 Hours at 350°F.                                                                            8       8       8                                         Tensile, psig       1750    1810    1650                                      Elongation, percent 135     180     200                                       Compression set,    30      44      41                                        percent - 70 hrs.                                                             at 300°F.                                                          

The halogen- and carboxyl-containing rubber, sample 1, readily curedusing the alkali metal carboxylate and amine-blocked isocyanate curesystem. Samples 2 and 3, vulcanized using a known soap/sulfur system,cured slower as evidenced by the lower tensile on press-cure and muchhigher compression set of the samples. This example demonstrates thatthe novel vulcanizable compositions obtain a given state of cure muchfaster than previously known or suggested compositions.

EXAMPLE III

A rubber containing 97.8 percent by weight of ethyl acrylate, 1.6percent by weight of 5-chloroacetoxymethyl-2-norbornene, and 0.6 percentby weight of methacrylic acid was cured using potassium stearatecatalyzed using a guanidine. The recipe and data were as follows:

    Rubber                    100                                                 Acrawax C                 2                                                   N550 Black                65                                                  Potassium Stearate        2.8                                                 Guanidine/isocyanate.sup.1                                                                              0.7                                                 1 - di(tetramethyl guanidine)/toluene                                           diisocyanate reaction product                                               Press-cure, 20' at 350°F.                                              Tensile, psig             1780                                                Elongation, percent       140                                                 Hardness, Durometer A     68                                                  Compression set,          35                                                  percent - 70 hrs.                                                             at 300°F.                                                              Post-Cure, 8 hrs. at 350°F.                                            Compression set,          19                                                  percent - 70 hrs.                                                             at 300°F.                                                          

The example demonstrates the use in the cure system of guanidinecatalysts employed as guanidine-isocyanate reaction products.

EXAMPLE IV

Acrylate rubbers having both halogen and carboxyl cure sites werevulcanized using potassium or sodium stearate or disodium azelate as thecurative and amine-blocked isocyanates as cure catalysts. The rubbercomposition used was as follows (in weight percent):

    Ethyl Acrylate            23.4                                                n-butyl Acrylate          75                                                  Methacrylic Acid          0.3                                                 Vinyl Benzyl Chloride     1.3                                             

The example demonstrates the utility of the amine-blocked isocyanate ascatalysts. The amine-blocked isocyanates must first break down to freethe amine for catalysis. Hence, these catalysts are slower acting thanthe use of free amines.

    __________________________________________________________________________                   1  2   3   4   5   6   7   8   9   10                          __________________________________________________________________________    Rubber        100 100 100 100 100 100 100 100 100 100                         Acrawax C     2   2   2   2   2   2   2   2   2   2                           TE-80.sup.1   2   2   2   2   2   2   2   2   2   2                           N550 Black    80  80  80  80  80  80  80  80  80  80                          Sodium Stearate                                                                             3.0 3.5 3.5 4.0 3.5 --  3.5 4.5 3.5 --                          Potassium Stearate                                                                          --  --  --  --  --  --  --  --  --  3.5                         Disodium Azelate                                                                            --  --  --  --  --  1.2 --  --  --  --                          Dimethylamine/toluene                                                                       0.7 1.0 --  --  --  --  --  --  --  --                          diisocyanate                                                                  Dimethylamine/p-                                                                            --  --  1.0 1.0 --  1.0 1.0 1.0 0.7 1.0                         chlorophenyl                                                                  isocyanate                                                                    Dimethylamine/m,p-                                                            dichlorophenyl--  --  --  --  1.0 --  --  --  --  --  --                      isocyanate                                                                    Dodecyl bromide                                                                             --  --  --  --  --  --  1.0 1.0 1.0 --                          Press Cure                                                                    (60 minutes at 320°F.)                                                 Tensile, psi  1040                                                                              1050                                                                              1080                                                                              1010                                                                              1100                                                                              1000                                                                              1100                                                                              930 1150                                                                              1150                        Elongation, percent                                                                         140 180 180 170 160 140 130 160 140 170                         Hardness, Durometer A                                                                       75  75  77  75  75  81  78  78  76  75                          Compression Set, percent                                                      (70 hrs. at 300°F.)                                                    Press-Cure    61  63  56  56  47  80  72  63  66  45                          Post-Cure.sup.2                                                                             40  55  30  42  26  53  40  39  36  26                          __________________________________________________________________________    1 - synthetic wax                                                             2 - 20 hours at 300°F.                                             

EXAMPLE V

An acrylate rubber consisting of interpolymerized units of 75.5% byweight n-butyl acrylate, 23% ethyl acrylate, 0.3% methacrylic acid, and1.2% by weight vinyl benzyl chloride was cured using varying amounts ofsodium stearate as the curative and dimethylamine-blocked p-chlorophenylisocyanate as the cure catalyst. Recipes, cure conditions, and resultsare given in the following table.

    __________________________________________________________________________                        1  2   3   4   5   6                                      __________________________________________________________________________    Rubber             100 100 100 100 100 100                                    Acrawax C          2   2   2   2   2   2                                      N550 Black         55  55  55  55  55  55                                     N881 Black         20  20  20  20  20  20                                     Sodium Stearate    2.3 2.3 2.3 2.0 2.5 2.5                                    Dimethylamine/p-chlorophenyl                                                                     0.6 0.8 1.0 1.0 0.6 1.0                                    isocyanate                                                                    Press-Cure (40 minutes at 310°F.)                                      Tensile, psi       1400                                                                              1400                                                                              1370                                                                              1370                                                                              1330                                                                              1150                                   Elongation, percent                                                                              250 240 240 240 230 230                                    Hardness, Durometer A                                                                            58  60  60  61  60  53                                     Compression Set, percent                                                                         64  64  53  59  65  64                                     (70 hrs. at 300°F.)                                                    Post-Cure (20 hours at 300°F.)                                         Tensile, psi       1300                                                                              1370                                                                              1300                                                                              1330                                                                              1310                                                                              1050                                   Elongation, percent                                                                              150 140 180 150 150 160                                    Hardness, Durometer A                                                                            67  66  65  67  68  60                                     Compression Set    30  31  27  34  26  40                                     (70 hrs. at 300°F.)                                                    __________________________________________________________________________

EXAMPLE VI

An acrylate rubber consisting of interpolymerized units of 47% by weightof ethyl acrylate, 46.5% by weight of n-butyl acrylate, 5% by weight ofethyl vinyl ether, 0.3% by weight of methacrylic acid, and 1.2% byweight of vinyl benzyl chloride was cured. The recipe used was: 100parts by weight acrylate rubber, 2 parts Acrawax C, 55 parts N550 black,20 parts N881 black, 2.0 parts sodium stearate, 1.0 partdimethylamine/m,p-dichlorophenyl isocyanate, and 1.0 part dodecylbromide. The press-cure properties obtained were 700 psi tensile, 70percent elongation, and 75 Durometer A hardness (cured 30 minutes at320°F.).

We claim:
 1. A composition comprising (1) an acrylate rubber comprising(a) from about 40 percent to about 99.8 percent by weight of an acrylateor mixtures of acrylates of the formula ##EQU1## wherein R' is selectedfrom the group consisting of an alkyl radical containing 1 to 18 carbonatoms, an alkoxyalkyl radical, alkylthioalkyl radical, and cyanoalkylradical each containing a total of 2 to about 12 carbon atoms in theradical, (b) from about 0.1 percent to about 30 percent by weight of ahalogen-containing monomer selected from the group consisting ofhalogen-containing vinylidene hydrocarbons and halogen-containing vinylmonomers wherein the halogen group is at least 2 carbon atoms removedfrom an oxygen atom, (c) from about 0.1 percent to about 20 percent byweight of a carboxyl-containing monomer, and (d) up to about 35 percentby weight of a non-halogen-containing and non-carboxyl-containingcopolymerizable monomer having a terminal vinylidene group, and (2) acure system consisting essentially of (a) from about 0.5 part to about 7parts by weight based upon 100 parts by weight of the rubber of analkali metal salt of an acid selected from the group consisting ofcarboxylic acids containing 2 to about 24 carbon atoms andorganophosphoric acids of the structure ##STR6## wherein M is an alkalimetal, y = 1 or 2, z = 1 or 2, and y + z = 3, and R is selected from thegroup consisting of an alkyl radical containing 1 to 24 carbon atoms, anaryl radical containing 6 to 24 carbon atoms, and an alkylphenoxypoly(ethyleneoxy)ethyl radical, and (b) from about 0.1 part to about 10parts by weight based upon 100 parts by weight of the rubber of anamine-blocked isocyanate wherein the amine has a dissociation constantof below 10 and is a secondary amine or guanidine.
 2. A composition ofclaim 1 wherein the acrylate rubber consists essentially ofinterpolymerized units of (a) an acrylate or mixtures of acrylateswherein R' is an alkyl radical containing 1 to about 10 carbon atoms oran alkoxy alkyl radical containing 2 to about 8 carbon atoms, (b) ahalogen-containing monomer(s) selected from the group consisting ofvinyl benzyl chloride, vinyl benzyl bromide,5-chloromethyl-2-norbornene, 5-bromomethyl-2-norbornene,5-β-chloroethyl-2-norbornene, vinyl chloroacetate, vinyl bromoacetate,allyl chloroacetate, vinyl-3-chloropropionate, vinyl-4-chlorobutyrate,vinyl-4-bromobutyrate, 2-chloroethyl acrylate, 3-chloropropyl acrylate,4-chlorobutyl acrylate, 2-chloroethyl methacrylate, 2-bromoethylacrylate, 2-iodoethyl acrylate, 4-chloro-2-butenyl acrylate,2-chloroacetoxyethyl acrylate and methacrylate, 2-chloroethyl vinylether, chloromethyl vinyl ketone, 2-chloroethyl vinyl ketone,5-chloroacetoxymethyl-2-norbornene, and5-(α,β-dichloropropionylmethyl)-2-norbornene, (c) a carboxyl-containingmonomer(s) selected from the group consisting of acrylic acid,methacrylic acid, ethacrylic acid, β,β-dimethyl acrylic acid, crotonicacid, 2-pentenoic acid, 2-hexenoic acid, maleic acid, fumaric acid,citraconic acid, mesaconic acid, itaconic acid, and3-butene-1,2,3-tricarboxylic acid, and (d) a copolymerixable monomerselected from the group consisting of vinyl acetate, allyl acetate,methyl and ethyl methacrylate, vinyl ethyl ether, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide,divinyl benzene, and diethylene glycol diacrylate.
 3. A composition ofclaim 2 wherein (2) (a) is an alkali metal salt of a monocarboxylic acidcontaining from about 6 to about 20 carbon atoms, said acid salt beingused in a level from about 1 part to about 5 parts by weight per 100parts by weight of acrylate rubber.
 4. A composition of claim 3 wherein(2) (b) is an amine-blocked isocyanate wherein the amine is a secondaryamine or a guanidine and the isocyanate is an aromatic isocyanate, saidamine-blocked isocyanate used in from about 0.3 part to about 5 parts byweight per 100 parts by weight of the acrylate rubber.
 5. A compositionof claim 4 wherein (1) is an acrylate rubber of (a) ethyl acrylate,n-butyl acrylate, or mixtures thereof, (b) vinyl benzyl chloride or5-chloroacetoxymethyl-2-norbornene, and (c) methacrylic acid.
 6. Acomposition of claim 5 wherein (2) (a) is an alkali metal salt ofstearic acid and (2) (b) is a dialkyl amine-blocked isocyanate whereinthe alkyl radicals contain 1 to about 6 carbon atoms and the isocyanateis a phenyl isocyanate or an aromatic diisocyanate.
 7. A composition ofclaim 6 comprising (1) an acrylate rubber of ethyl acrylate, vinylbenzyl chloride, and methacrylic acid, and (2) a cure system consistingessentially of (a) sodium stearate and (b) a dimethylamine-blockedm,p-dichlorophenyl isocyanate.
 8. A composition of claim 6 comprising(1) an acrylate rubber of ethyl acrylate, n-butyl acrylate, vinyl benzylchloride, and methacrylic acid and (2) a cure system consistingessentially of (a) sodium or potassium stearate and (b) adimethylamine-blocked isocyanate wherein the isocyanate isp-chlorophenyl isocyanate, m,p-dichlorophenyl isocyanate, or toluenediisocyanate.
 9. A composition of claim 8 wherein (2) (a) is sodiumstearate and (2) (b) is dimethylamine-blocked p-chlorophenyl isocyanate.10. A composition of claim 5 comprising (1) an acrylate rubber of ethylacrylate, 5-chloroacetoxymethyl-2-norbornene, and methacrylic acid and(2) a cure system consisting essentially of (a) potassium stearate and(b) tetramethyl guanidine-blocked toluene diisocyanate.